The present invention relates generally to operations performed in conjunction with subterranean wells and, in an embodiment described herein, more particularly provides a tool for retrieving items of equipment from within tubular strings in subterranean wells.
It is common for items of equipment to be releasably secured within tubular strings in subterranean wells. For example, a flow control device, such as a safety valve, may be releasably secured in a tubing string by means of a lock mandrel attached thereto. The lock mandrel typically includes an anchoring mechanism, which prevents displacement of the mandrel relative to the tubing string, and at least one seal, which engages a seal bore of the tubing string.
Over time, it may become very difficult to release the lock mandrel from its engagement with the tubing string in order to retrieve the lock mandrel and safety valve for service, replacement, etc. Often, the lock mandrel is difficult to displace relative to the tubing string due to the seal adhering to the seal bore. Thus, it is sometimes necessary to apply a very large amount of force to the lock mandrel to get it free from the tubing string. This may be accomplished by, for example, using jars to repetitively apply an impact to the lock mandrel. However, where the lock mandrel and/or safety valve are relatively heavy, where it is desired to prevent damage to the lock mandrel from impact, or where the lock mandrel is very stuck in the tubing string, it may not be desirable or effective to use the jarring method to retrieve the lock mandrel and safety valve.
Therefore, it may be seen that it would be very desirable to provide another method for retrieving an item of equipment from within a tubular string in a subterranean well. It is accordingly an object of the present invention to provide such a method and an associated retrieval tool.